A communication system is formed, at a minimum, of a set of communication stations interconnected by way of a communication channel. At least a first communication station of the set of communication stations forms a sending station, and at least another of the communication stations forms a receiving station. Data is communicated by the sending station to the receiving station by way of the communication channel. A sending station, if necessary, converts the data into a form to permit its communication upon the communication channel. And, the receiving station operates to recover the informational content of the data communicated thereto.
Many different types of communication systems have been developed and implemented to effectuate many different types of communication services in which data is communicated between separate communication stations. And, as advancements in communication technologies permit, improvements to such communication systems, as well as the development and implementation of new types of communication systems, have been, and continue to be, made.
A radio communication system is an exemplary type of communication system. Communication channels defined in a radio communication system are defined upon radio links extending between the communication stations of the radio communication system. Because radio links are utilized upon which to define communication channels, conventional wireline connections, otherwise required upon which to define the communication channels, is obviated. And, as a result, the infrastructure costs associated with radio communication systems are generally less than the infrastructure costs associated with a conventional, wireline communication system. And, use of the radio links upon which to define communication channels permits a radio communication system to be implemented as a mobile communication system.
A cellular communication system is a type of radio communication system. Radio telephonic communications are effectuable by way of a cellular communication system. And, the networks of various types of cellular communication systems have been installed throughout significant parts of the populated portions of the world.
In general, a cellular communication system includes a fixed-network infrastructure that is installed throughout a geographical area which is to be encompassed by the communication system. The fixed-network infrastructure includes a plurality of spaced-apart, fixed-site base transceiver stations. Each of the base transceiver stations defines an area, referred to as a cell, and from which the cellular communication system derives its name. The base transceiver stations are sometimes said to form part of a radio access network (RAN) part of the communication system. And, groups of the base transceiver stations are controlled by control devices that also form parts of the radio access network part of the communication system.
The radio access network part is connected to a core network, such as a PSTN (public-switched telephonic network) or a PDN (packet data network), such as the internet. Data sources, such as computer servers, as well as telephonic stations, and other communication devices are, in turn, coupled to the core network to be capable of communication therethrough.
A user communicates in the cellular communication system through the use of a mobile station, constructed to be operable therein. The mobile station forms a portable transceiver capable of sending and receiving data-containing signals upon radio channels defined upon the radio links allocated to the communication system. Due to the spaced-apart positioning of the base transceiver stations, the mobile station is generally able to communicate with at least one of the base transceiver stations when positioned at any location within the geographical area encompassed by the communication system.
The radio channels upon which the data-containing signals are communicated are susceptible to distortion, caused, e.g., by fading conditions. If the distortion is not corrected, the informational content of the data that is communicated during operation of the communication system cannot adequately be recovered.
Various techniques are utilized to compensate for, or otherwise overcome, the distortion introduced upon the data during its communication upon a radio channel.
Encoding of the data pursuant to an encoding scheme is sometimes performed. The encoding of the data increases the likelihood that the informational content of the data can be recovered.
Space diversity also is sometimes utilized. Space diversity is created through the use, at a sending station, of more than one transmit antenna transducer from which the data is transduced. Spatial redundancy is thereby provided. The antenna transducers are typically separated by distances great enough to ensure that the information communicated by the respective ones of the antenna transducers fades in uncorrelated manners. Receiving stations sometimes also include more than one spaced-apart receive antenna transducers.
Antenna weightings are sometimes utilized by which to weight data-containing signals provided to the respective ones of the antenna transducers. The antenna weightings are selected, and dynamically reselected, in manners intended to optimize the communication of the data. For instance, the antenna weightings are selected to maximize the energy levels of the data-containing signal, when received at the receiving station. A spatial diversity scheme that utilizes antenna weightings requires feedback to dynamically reselect, or otherwise alter, the antenna weightings of the respective antenna transducers. If fading conditions on the communication channel are significant, the reliability of the feedback information might not be of a level appropriate to benefit the improvement of communication quality levels of the communication of the data. Additionally, and sometimes even more significantly, the feedback information cannot be relied upon, due to its untimeliness. For instance, particularly in high-velocity situations, the feedback information is delivered too late to be reliable. Other aspects also affect the reliability. For example, the quantity of feedback (number of bits used to convey the feedback) determines its accuracy. Also, if tracking algorithms used by the receiver to “track” the progression of the weights, these tracking algorithms perform less reliably in fast fading.
A transmit diversity scheme that takes into consideration the reliability and timeliness of feedback information and would therefore be advantageous.
It is in light of this background information related to communication systems that utilize transmit diversity that the significant improvements of the present invention have evolved.